I had well over 100 on my X3. I could pretty much see the previous owners life story, and had phone numbers for their family and friends (off the SMS).

I spoke to the dealer about this, and they had absolutely no idea how to bulk delete. I did say that it was a breach of the UK Data Protection because of some of the information.....

Anyhow, I had to spend an hour or more going through and deleting them one by one.